I'd never heard of UTC - which is Coordinated Universal Time - or Zulu time, nor did I know how they'd be related. (Hey, what can I say - I'm a geek, but not that kind of geek.) Zulu time turns out to have nothing to do with South-African airports:

The UTC time zone is sometimes denoted by the letter Z – a reference to the equivalent nautical time zone (GMT), which has been denoted by a Z since about 1950. The letter also refers to the "zone description" of zero hours, which has been used since 1920 [..]. Since the NATO phonetic alphabet and amateur radio word for Z is "Zulu", UTC is sometimes known as Zulu time. This is especially true in aviation, where Zulu is the universal standard.

I still don't get why "local" time and "president" time are different things though. Although I guess it's just adjusted all the time when he travels, so some staffer doesnt accidentally wake him up when he, the staffer I mean, finds the Situation Room fax machine-cum-copier not working and calls up the Prez to ask what the code was again, forgetting that the man is in Manila and it's 4 AM for him right now?